1. Technical Field
The present invention relates to information processing systems that operate with a low power consumption, and more particularly to a portable information processing system such as a notebook computer.
2. Description of the Related Art
As a result of the recent technological innovation, small-size and lightweight portable computers have become common. When such portable computers are used outdoors, electric power is supplied to them with batteries. However batteries mounted on portable computers are restricted to small-size batteries. Thus the amount of operation time of personal computers with one charge of the batteries is short. Consequently, various kinds of devices are provided for reducing the consumption of power in many portable computers.
A suspend/resume function is one of such devices. When the suspend/resume function operates, the computer enters into a suspend mode in response to a situation such as one in which the activity of an I/O device is not detected for a certain time. In the suspend mode all tasks are suspended and the main memory saves data which will be required later for resuming the tasks. In the suspend mode the main memory and the video memory (VRAM) are powered on, but the CPU or the like are powered off. However, portable computers have a drawback in that the power of batteries is consumed when the suspend mode continues for a long time with only the support of the suspend/resume function, resulting in the contents of the memory and the VRAM being erased.
Therefore, portable computers which are supported with a hibernation mode, such as the LTE Lite/25 manufactured by Compaq Company (Compaq and LTE are registered trademarks of Compaq Computer Corporation), have been proposed and marketed. When the hibernation mode is enabled, the computer enters a low battery state. Otherwise, when the suspend mode continues for a certain time, the computers enter hibernation mode after saving all the data required for resuming the task later onto the hard disk. In hibernation mode, the whole system, including the memory and the VRAM, is powered-off. When users power-on the system later, the data stored in the hard disk is restored in the memory and the VRAM and the tasks which had been suspended are automatically resumed. The series of operations accompanying power-on are also referred to as wake-up.
Conventional information systems have a drawback in that if a floppy disk drive (FDD) is resumed or woken-up and powered-on after a floppy disk has been exchanged during a suspend or hibernation mode in which a floppy disk controller (FDC) and the FDD are powered off, the FDD accesses the new floppy disk using the file allocation information in the old floppy disk, thereby destroying the data on the new floppy disk.